1. Technical Field
The present invention relates to a liquid detection device and method that detects the presence or absence of liquid by driving a liquid detecting portion and also to a liquid ejecting apparatus that uses the liquid detection device.
2. Related Art
For example, a technology for detecting the presence or absence of ink in an ink cartridge is known as a liquid detection device. In the above technology, a piezoelectric element is used as a sensor, and then the presence or absence of ink is detected using a counter electromotive voltage waveform that is obtained after the piezoelectric element is driven. Specifically, an ink flow passage is provided adjacent to the piezoelectric element, and it is determined whether a counter electromotive voltage waveform output from the piezoelectric element because of residual oscillation coincides with a resonance frequency that is obtained when the ink flow passage is filled with ink or the counter electromotive voltage waveform coincides with a resonance frequency that is obtained when the ink flow passage is not filled with ink, so that it is determined whether the amount of ink contained in the ink cartridge is equal to or above a predetermined amount, which is, for example, described in JP-A-2001-146030.
However, because the counter electromotive voltage waveform oscillates with respect to the termination voltage at the time when application of a driving signal to the piezoelectric element is completed, when a low frequency component is intended to be removed using a high-pass filter that includes a capacitor portion, there is a problem that the low frequency component cannot be sufficiently removed until the capacitor portion is charged by the termination voltage. In addition, when the counter electromotive voltage waveform is measured after the capacitor portion has been charged, there is a problem that an oscillation attenuates, an S/N ratio deteriorates and, hence, the detection accuracy decreases.